Reg. KVM
KVMs are only a control between two computers you do need the monitor, mouse and keyboard to use a KVM. and as for remote use of a computer you will need a monitor if using windows as you will need to see from that system each time it is rebooted.
I would go get a new monitor and be alot more careful with it as they are not intended to be used as footballs. There ways to get windows to boot and login via remote but the setup of this would depend on you O/S, NIC, Router and even the tower as some tear one companies eg DELL, HP, Aser, Toshiba and so-on will block some functions of remote use on some of their systems I have seen where HP has blocked remote use on some of their "Topend" work stations making I.T. Techs mad as hornets and having to buy additional software that works on a diffrent proto all-together meaning hours of waisted time and money. Dell is alittle better for this as they build more for the "Need now networkers" work remotly from home and new to the PC world market.
I would would say getting Samsung SyncMaster 17" CRT (as they are harty monitors that work well and will refresh up to 100 Mhz a second) in you prefered colour and a KVM switch with a "on box" control as the keyboard control KVMs are cheaper, they are harder to use at first and often anger new computer users; the monitor will very where you live as some states and provinces in Canada and the U.S. have "hiden taxs" on them the KVM should be around $95.00 - $130.00 U.S. but if you want to try a keyboard control KVM Linksys makes a "easy to use" one for about $50.00 U.S. the only problem with it is getting you switch comand timings down and you use the left shift and the right shift keys to toggel into scan mode and the spasbar to stop on the system you want... Once you get your timings down on that switch it is a very good KVM for the price. I have the Linksys 2-Port KVM Switch that is a keyboard control on my two main computers and home. For shomeone like me that plays drums and alot of other things it works real good and I got switching down in less then a day.
As far as the Laptop being used as a monitor unless you have a second video in port that some Dells do have it would not be easy to do, you can look for a USB monitor in cable but I would have to say that would cost a fair size greenback same with using a USB external GPU device as they start at about $270.00 U.S. and you could all-most get the KVM and monitor for that.
There also maybe a way to use your tower as a slave to your Laptop via a USB network cable but I am not aware of the way that would be done off-hand as I don't use USB networking that maybe the cheapest way to look into first, but if Dell has limitem the use of your USB ports that may not be feasable either. Call Dell about that one ask for a ranking tech and the first level only work with a database and would not know that off hand without going through their info bank most often missing the info all together or ton looking in the right section.
Good luck.